An unsensitised Rh-negative woman undergoes suction evacuation for a missed miscarriage at 9 weeks of gestation. Paternal blood group is unknown and she is Rh negative. What anti-D regimen is appropriate?

• A No anti-D is required before 12 weeks
• B 50 micrograms (mini-dose) within 72 hours ✓
• C Full 300 micrograms dose within 72 hours
• D 1200 micrograms immediately, repeated weekly

Explanation

Before 12 weeks the fetal red cell volume is small, so a mini-dose of 50 micrograms (250 IU) given within 72 hours of the event adequately covers any fetomaternal bleed. Beyond 12 weeks, and for procedures like amniocentesis at any gestation, the standard adult dose of 300 micrograms (1200 IU) is required because larger fetomaternal haemorrhage is possible. Option A ignores that even first trimester events can sensitise.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.